Hair is composed of keratin, a cystein-rich fibrous protein. The high amount of acidic sulfhydryl-groups in the protein consequently leads to a net anionic charge of the hair cuticle under the pH-conditions of a regular shampoo. This anionic charge of the hair opens perspectives for a surface treatment with cationic polymers with the goal to improve the physical properties of the hair. Such cationic polymers have the ability to form adherent films on the anionic surface of the hair cuticle. This surface treatment of the hair is known as conditioning. Hence, cationic polymers are widely used as conditioners to facilitate wet and dry hair combing, to suppress static charging or to facilitate the detangling of the hair.
The demands to suitable cationic polymers are diverse. They have to exhibit an immediate effect in order to be judged positively by the applicant and their properties have to be balanced carefully in order to provide the desired effects for the specific application without exhibiting undesired side-effects. For example, on one hand they have to exhibit a sufficient adhesion to the hair in order to prevent removal during the rinsing process of the hair, on the other hand they should not form multilayer films with subsequent overload. Furthermore, they have to be compatible to aqueous systems in order to enable the production of suitable cosmetic formulations but at the same time the films shall have an intrinsic resistance towards the uptake of humidity on the hair.
The two characteristics of a cationic polymer which mainly determine the character of the films are the molecular weight and its level of cationic charge. Depending on the hair type and the desired applications those two characteristics have to be adjusted carefully in order to obtain the desired conditioning effects.
As the skin also provides a slightly acidic surface, similar considerations can also be applied to topical applications. In these applications it is known that cationic polymers can form adherent films on the skin, thereby promoting effects like softness. In cases where the film reduces the trans-epidermal water loss, cationic polymers can improve moisture retention and skin humidity.
As for the hair, the film forming properties of suitable cationic polymers have to be adjusted finely in order to exploit the full potential of skin conditioning without overload of the surface.
The cationic conditioners currently employed in formulations for the treatment of keratin-containing substrates are based on different polymeric backbones. They mainly consist of cationic polymers, proteins or protein derivatives or fatty quaternary ammonium compounds. Commonly used cationic polymers include quaternary nitrogen-containing hydroxyethyl cellulose compounds, copolymers of vinylpyrrolidone and dimethylamino-ethylmethacrylate, and amino functional polydimethyl-siloxane. Hydrolyzed animal protein has been frequently used as a keratin conditioner. Also used are natural products such as collagen and casein.
The beneficial properties of co-polymers based on dimethyl diallylammonium chloride and acrylamide have been employed in toilet bars (EP 0,308,189), the use of hydroxyethyl cellulose cross linked with dimethyl diallylammonium chloride has been described in EP 0,308,190 and U.S. Pat. No. 4,803,071.
While these polymers provided acceptable solutions with respect to handling and cosmetic performance they exhibit the disadvantage of a poor biodegradability with the consequence of accumulation in the environment.
As a consequence of the growing environmental awareness, polymers based on natural backbones have been developed in order to provide an improved inherent biodegradability. These natural backbones initially were found in the class of polysaccharides such as cellulose and polypeptides such as guar.
Hair care compositions comprising cationic cellulose are well known. For example hydroxypropyl trimethyl ammonium chloride ethers of cellulose, widely known as Polyquaternium-10, have been used in conditioning or shampoo compositions (see U.S. Pat. No. 5,288,484, respectively U.S. Pat. No. 4,205,063) and can be considered state-of-the art treatments for keratinous substrates. Due to its strong interaction with the hair cuticle Polyquaternium-10 very well improves the combing properties on the hair. On the other side it tends to accumulate on the hair reducing its manageability.
Cationically modified guar gums such as hydroxypropyl trimethyl ammonium chloride ethers of guar have also been used extensively in hair care compositions. While their conditioning capacity is limited, quaternized Guar Gums contribute to a creamy and cosmetic perception of cosmetic products containing this cationic species. U.S. Pat. No. 4,292,212 therefore describes the use of this material in a shampoo crème rinse while U.S. Pat. No. 4,676,978 describes the use of this material in a shampoo.
As the quaternization of natural polymers reduced their biodegradability, non-ionic cellulose materials have been developed and can also be found in hair care formulations. E.g. U.S. Pat. No. 4,786,494 describes shampoo compositions which comprise a non-ionic cellulose ether compound and a hair conditioning composition comprising hydroxyethyl cellulose.
In the past years liquid modified starch materials have been developed in order to find a remedy for the handling disadvantages powder state conditioners. E.g. EP 1,051,967 describes cosmetic compositions containing oxidatively degraded modified starches and methods of stabilizing liquid formulations of these modified starches by addition of urea and/or α-hydroxy acids. Another application claims comparable liquid formulations of modified starches and their use in the treatment of keratinous substrates (see WO 0,139,721).
While the liquid and stable formulations available by these technologies provide the benefit of easy handling in production scale applications, the cosmetic formulations based on the claimed liquid starch solutions, however, have the disadvantages that in many cases they are of lower performance than comparable cosmetic formulations with other state-of-the-art modified polymers. Especially the immediate performance of the current cationic starch conditioners is insufficient in comparison to Polyquaternium-10 and therefore the evaluation of the applicant is not in favour of products containing these conditioners. In addition the stabilized liquid starch solutions are prone to microbiological deterioration and require preservative stabilization (see WO 0,139,721).
Various modifications of starch polymers and cosmetic compositions containing these starch derivatives have been developed in the past years for specific applications or to find a remedy to the low conditioning performance of the marketed cationic starch conditioners.
EP 0,988,023 discloses skin care compositions containing hydrophobic starch modified with calcium salts of dicarboxylic acids. These modified starches are described to improve the aesthetic appearance of the formulation.
Cosmetic compositions containing amphoteric amino-multicarboxylate modified starch is disclosed for modifying the rheological properties of cosmetic compositions in EP 0,689,829 and U.S. Pat. No. 4,080,310 discloses the use of a cationic starch in an amphoteric conditioning shampoo.
EP 1,598,046 describes mixtures of natural and synthetic polymers to form fixative films. As natural polymer chemically modified starches are claimed in combinations with e.g. Polyquaternium-4.
A method and composition to achieve stable colour of artificially coloured hair employing amylase containing starch is described in EP 1,568,351 and US 2005/0287,106 describes the use of modified starches to improved the efficacy of shaving formulations.
A further attempt to eliminate disadvantages of cationic starch polymers is described in US 2006/002,880. In this application, cosmetic formulations containing combinations of low molecular weight quaternized starches with co-acervates have been described. According to this patent application polyethoxylated anionic surfactants serve as co-acervates and the molecular weight of the quaternized starch polymer is <200.000 Da. This application addresses the topic of improved conditioning properties of skin and hair and describes the use of starch polymers of different sizes and degree of quaternization. However, it does not investigate into mixtures of modified starch polymers. Further, it has been found that the claimed formation of co-acervates can lead to the formation of turbidity and can therefore be contraindicated for the formulation of transparent formulations.
Therefore there remains a need for a cosmetic and/or dermatological composition which is in particular suitable for the treatment of keratinous substrates such as hair, animal hair, skin or nails which:                a) meets or exceeds the conditioning performance of state-of-the-art formulations, characterized by the immediate wet and dry combing performance, the static charging of the hair and the detangling performance        b) is flexible towards the specific demands of different types of keratinous substrates        c) can be manufactured easily with stable liquid formulations of inherently biologically degradable polymers        d) can be removed easily from the keratinous surface in order to avoid accumulation and consequently a poor manageability of the hair.        
In addition, a growing demand for cosmetic formulations which do not contain traditional preserving agents exists. As many raw materials with conditioning properties and especially their aqueous systems are prone to microbiological contaminations they contain traditional preservatives for the in-can stabilization. Hence, the formulation of preservative-free systems is difficult according to the state-of-the-art.
Surprisingly, it has been found that the liquid modified starch polymers employed in compositions according to the present invention can be stabilized against microbiological contamination and therefore exhibit excellent solutions to deficiencies of the state-of-the-art.